1. Field of the Invention
The invention relates to a video signal transmitting device for transmitting video signals between a display and a computer device, more particularly to a computer system that has both analog and digital video signal output functionality to enable dual screen displaying on a digital display and an analog display, and to a computer device and a video signal transmitting device of the computer system.
2. Description of the Related Art
Conventional computer devices generally use a video signal transmission line to connect to a display so as to transmit video signals to the display. Currently, there are two types of video signals, i.e., analog video signals and digital video signals. A conventional analog video signal transmission port is D-Sub, which is used, e.g., in a conventional cathode ray tube (CRT) display. A digital video signal transmission port is a digital visual interface (DVI) for use in, e.g., a liquid crystal display.
Although the image display quality of digital video signals is better and will become a mainstream in the future, since analog video devices have been popular for a long time, many users still have displays or computer devices that use analog video signals. In order to be compatible with specifications of existing analog video signal transmission ports, recently launched displays or computer devices, in addition to having a digital video signal transmission port, still need to be provided with an analog transmission port or to be used in conjunction with a video signal transmission line having an adapting or converting function, such as DVI TO VGA.
Furthermore, with the image processing capability of the conventional computer device becoming more and more powerful, the computer device can now support dual screen output displaying via a one-to-two video signal transmission line or two video signal transmission ports provided at a rear part of the computer device. However, dual screen output displaying which uses a one-to-two video signal transmission line requires the video signal transmission ports of two associated displays to have the same specification, i.e., both are for either analog video signals or digital video signals. Dual screen displaying is not possible with one display device supporting analog video signals and the other supporting digital video signals, which can be inconvenient to the user.